hybrid offspring, some degree of sterility. Nevertheless, the several
domesticated races descended from them are now all, as far as can be
ascertained, perfectly fertile together. If this reasoning be trustworthy, and
it is apparently sound, we must admit the Pallasian doctrine that long-
continued domestication tends to eliminate that sterility which is natural to
species when crossed in their aboriginal state.

ON INCREASED FERTILITY FROM DOMESTICATION AND CULTIVATION.

Increased fertility from domestication, without any reference to crossing, may
be here briefly considered. This subject bears indirectly on two or three
points connected with the modification of organic beings. As Buffon long ago
remarked (16/31. Quoted by Isid. Geoffroy St. Hilaire 'Hist. Naturelle
Generale' tome 3 page 476. Since this MS. has been sent to press a full
discussion on the present subject has appeared in Mr. Herbert Spencer's
'Principles of Biology' volume 2 1867 page 457 et seq.), domestic animals
breed oftener in the year and produce more young at a birth than wild animals
of the same species; they, also, sometimes breed at an earlier age. The case
would hardly have deserved further notice, had not some authors lately
attempted to show that fertility increases and decreases in an inverse ratio
with the amount of food. This strange doctrine has apparently arisen from
individual animals when supplied with an inordinate quantity of food, and from
plants of many kinds when grown on excessively rich soil, as on a dunghill,
becoming sterile: but to this latter point I shall have occasion presently to
return. With hardly an exception, our domesticated animals, which have been
long habituated to a regular and copious supply of food, without the labour of
searching for it, are more fertile than the corresponding wild animals. It is
notorious how frequently cats and dogs breed, and how many young they produce
at a birth. The wild rabbit is said generally to breed four times yearly, and
to produce each time at most six young; the tame rabbit breeds six or seven